An ordinary egg can be approximated as a 5.5- cm diameter sphere whose properties are roughly k = 0.6 W/m·k and α = 0.14 × 10-6 m2 /s. The egg is initially at a uniform temperature of 4°C and is dropped into boiling water at 97°C.

Taking the convection heat transfer coefficient to be h = 1400 W/m2 ·K, determine how long it will take for center of the egg to reach 70°C.

The time required to reach the center temperature of egg at 70 °c  is     0.3 sec.

Explanation:

Given data

Diameter (d) = 5.5 cm = 0.055 m

K = 0.6

h= 1400

Initial temperature = 4 °c= 277 K

Ambient temperature = 97 °c= 370 K

Center temperature T = 70°C = 343 K

Thermal diffusivity  α =   ×

We know that

× =

4.28 ×

We know that from the lumped parameter  analysis

Put all the values in above equation we get

0.29 = 0.965 × t

t = 0.3 sec

Therefore the time required to reach the center temperature of egg at 70 °c is 0.3 sec.

layers of the earth affect the waves and these effects are seen on instruiments such as seimometers